if you want to have some idea's about what to make, you can also try a youtube search on 'miditron'. As midisense and miditron share some features and miditron seems to exist a bit longer, it is easier to find something..

i like airpercussion, but wish i could see more of it
the game controller midisense units look cool too, but on a functional level don't seem too ideal (no velocity sensitivity). would be a great controller for ableton, triggering phrases and samples.

http://fr.youtube.com/watch?v=RpSm5Hw-tpQ"My friend's project I am helping out with. Here we test the light sensors with a flashlight and my fingers.From RIGHT to LEFT:1. Oscillator note (5 different notes triggered by certain values coming in from the sensor)2. Note stepped finetune (not working with the rest that well yet)3. Pad trigger (3 pad samples that loop, triggered by certain values that come from the sensor)4. Pad filter cutoff5. Beat forward/reverse (it should play forwarded when light is fully on the sensor, right now it puts the sample in reverse)6. Sample End Position (gives funny glitches, alas this is not going in the project, we just needed to hook it up to something)"